Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Techniques

Background:

• Understanding electron density fluctuations is crucial for plasma confinement in fusion devices.
• Previous diagnostic methods had limitations in simultaneously measuring radial and poloidal correlations.

Purpose of the Study:

• To design, install, and validate a novel X-mode polarized V-band reflectometry system.
• To enable simultaneous radial and poloidal correlation measurements of electron density fluctuations.
• To characterize plasma turbulence in the Experimental Advanced Superconducting Tokamak (EAST).

Main Methods:

• Utilized X-mode polarized V-band (50-75 GHz) waves for reflectometry.
• Employed two frequency synthesizers (12-19 GHz) up-converted to V-band.
• Implemented a single pyramidal antenna for wave launching and two poloidally separated antennas for reception.
• Applied ray-tracing code and cross-phase spectrum analysis for data interpretation.

Main Results:

• Successfully measured a radial correlation length of approximately 1.5 cm in ohmically heated plasma.
• Estimated the fluctuation velocity perpendicular to the magnetic field in the plasma core to be between -1 km/s and -3 km/s.
• Demonstrated the system's capability for both radial and poloidal correlation measurements.

Conclusions:

• The newly developed reflectometry system is effective for diagnosing electron density fluctuations in EAST.
• The measurements provide valuable insights into plasma turbulence and transport mechanisms.
• This diagnostic advancement contributes to the understanding and control of fusion plasmas.